With the development of the semiconductor industry, the application of well-known Hall effect elements can be utilized in various semiconductor devices, in particular Hall-effect sensors. Such integrated Hall-effect sensors can be fabricated in accordance with well-known silicon planar process technology. Integrated Hall-effect sensors can be operated based on what can be referred to in the art as “Hall-effect technology.” Such Hall-effect technology can provide solutions for reliable solid-state magnetic switching and linear magnetic sensing. Hall-effect magnetic sensors can convert energy stored in the magnetic field to an electrical signal by means of the Hall-effect in order to sense position of a moveable object. Generally, the Hall-effect can occur when a conductor carrying electrical current is placed in a magnetic field. Integrated Hall-effect sensors can be utilized for automotive, consumer, medical and industrial applications.
Furthermore, the Hall element can be a basic component of the Hall-effect magnetic sensors and supplied by an electrical power source. The Hall element can be constructed from a thin sheet of conductive material with output connections perpendicular to the net direction of electrical current flow. When the magnetic field is applied normal to the plane, approximated as the thin sheet of electrical current flow through the Hall element, an electric field responds to counteract deflection of charge carriers due to the Lorentz force. The counteracting electric field is commonly referred to as the Hall field. The development of the Hall field results from the necessity of charge neutrality in the thin conducting sheet, in a direction perpendicular to the direction of current flow. The Hall field present between the output connections can be measured as a Hall voltage, which can be orthogonal to both the magnetic field and the electrical current flow. Such Hall voltage can be directly proportional to the magnetic field, in particular magnetic responsivity, and can be measured to sense magnetic flux density.
Hall-effect elements can be fabricated using a semiconductor material such as silicon. A Hall-effect element can include two bias contacts and two sensing contacts that can be formed by diffusing impurities into the semiconductor body incorporating a Hall-effect element. Metal conductors can be deposited and patterned on the surface of said semiconductor body to provide electrical connections to the Hall element. The diffused impurities raise the conductivity of the silicon in the localized regions of the contacts to provide ohmic characteristics at the interface of the silicon and the metal interconnects. The high-conductivity diffused regions that facilitate the contacts act approximately as equipotential regions within the bulk of the Hall effect element. The electric field must tend to zero along an equipotential boundary. Accordingly, the Hall field is diminished near the high conductivity diffused regions at the contacts. Deflection of mobile charge carriers occurs, in accordance with the Lorentz force, in the region of diminished Hall field near the contacts. The diminution of the Hall field and consequential deflection of mobile charge carriers in the region of a contact can be referred to as the shorting effect, and can be quantified as the shorting factor in a mathematical description of the Hall voltage. A common technique of prior art is to minimize the area of the contacts in order to minimize the shorting factor, thereby maximizing the Hall voltage.
Hall Offset can be measured as a differential voltage, at the output sensing contacts, in the absence of a magnetic field. Geometrical irregularities in the contact locations and shape can produce Hall offset. Processing tolerances effect the placement accuracy and geometry control of the contacts, so that there is a practical limit to contact size reduction imposed by Hall offset considerations. Ultimately, contact size is chosen on the basis of maximizing the Hall voltage-to-offset ratio.
It is well established in the literature that no particular geometrical shape or contact configuration can improve magnetic responsivity of single-plate Hall elements that are constructed using identical processes and materials. In the prior art, maximization of the Hall voltage-to-offset ratio is limited to reducing the Hall offset through precise control of geometrical symmetry. Other techniques can be applied to reduce Hall offset such as: averaging the output signals of a plurality of Hall elements that are arranged geometrically in a common centroid layout, the use of trimming networks or by averaging output signals obtained with multiple bias configurations; the so called current spinning method.
A need therefore exists for an improved Hall-effect magnetic sensor with higher magnetic responsivity, an improvement which can be provided by a parallel arrangement of two semiconducting layers, one n-type and one p-type, magnetically coupled across a nearly zero-bias depletion region. A nearly zero-bias depletion region herein includes any bias induced depletion layer that does not cause significant diffusion current to pass between the n-type and p-type layers. Such Hall-effect magnetic sensor is described in greater detail herein.